An effective approach to linear and angular position determining systems has been shown in my U.S. Pat. No. 4,035,762, issued on July 12, 1977. Such patent describes various embodiments for measuring a position along a line, either straight or curved, or on a plane or other curvilinear surface, with a high degree of accuracy at a reasonable cost. The embodiments described therein generally require two relatively movable members. In a particular embodiment one member may comprise a driver transducer and a delay line, both fixedly positioned, and a second member may comprise a receiver transducer which is movable with respect to the fixed driver transducer and the delay line. The resolution of the displacement measurement depends upon the phase shift experienced by a continuous elastic wave travelling once along a single delay line element in one direction only, parallel to, or coincident with, the distance to be measured. If position with respect to more than one axis is required, a plurality of such delay elements are used for such purpose.
It is desirable to reduce the number of delay elements in multi-axis systems in order to simplify the structure thereof as much as possible and to reduce the cost by requiring the use of fewer precision components while, at the same time, still providing high resolution. Moreover, in single-axis applications it is desirable to obtain much higher resolutions than presently available while still using the same components without changing either the frequency of the driver signal or the velocity of propagation in the delay medium.